language: C++ 4.7.2 (gcc-4.7.2)
date: 525 days 20 hours ago
link:
visibility: public 
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#include <iostream>
#include <boost/variant.hpp>
 
struct Cat{
  void speak() const{ std::cout << "meow\n"; }
  void cat_extra() const{ std::cout << "Special cat move!\n"; }
  ~Cat(){ std::cout << "Cat died\n"; }
};
 
struct Dog{
  void speak() const{ std::cout << "wuff\n"; }
  void dog_extra() const{ std::cout << "Special dog move!\n"; }
  ~Dog(){ std::cout << "Dog died\n"; }
};
 
struct Bird{
  void speak() const{ std::cout << "chirp\n"; }
  void bird_extra() const{ std::cout << "Special bird move!\n"; }
  ~Bird(){ std::cout << "Bird died\n"; }
};
 
struct Fish{
  void speak() const{ std::cout << "blub\n"; }
  void fish_extra() const{ std::cout << "Special fish move!\n"; }
  ~Fish(){ std::cout << "Fish died\n"; }
};
 
struct speak_visitor
    : boost::static_visitor<void>
{
    template<class Animal>
    void operator()(Animal const* p) const{
        p->speak();
    }
};
 
struct extra_visitor
    : boost::static_visitor<void>
{
    void operator()(Cat const* p) const{
        p->cat_extra();
    }
    void operator()(Dog const* p) const{
        p->dog_extra();
    }
    void operator()(Bird const* p) const{
        p->bird_extra();
    }
    void operator()(Fish const* p) const{
        p->fish_extra();
    }
};
 
struct delete_visitor
    : boost::static_visitor<void>
{
    template<class Animal>
    void operator()(Animal const* p) const{
        delete p;
    }
};
 
int main(){
    typedef boost::variant<Cat*, Dog*, Bird*, Fish*> variant_type;
    variant_type var;
    speak_visitor sv;
    delete_visitor dv;
    extra_visitor ev;
 
    var = new Cat();
    var.apply_visitor(sv);
    var.apply_visitor(ev);
    var.apply_visitor(dv);
 
    var = new Dog();
    var.apply_visitor(sv);
    var.apply_visitor(ev);
    var.apply_visitor(dv);
 
    var = new Bird();
    var.apply_visitor(sv);
    var.apply_visitor(ev);
    var.apply_visitor(dv);
 
    var = new Fish();
    var.apply_visitor(sv);
    var.apply_visitor(ev);
    var.apply_visitor(dv);
}